Coating compositions applied to floors such as made of wood, concrete, vinyl tiles, rubber tiles require good workabilities upon their applications. Furthermore, films formed after dryness also require to have good gloss, to be hardly stained with black heel marks by shoes, and to have good durability. In addition to these properties, they also require detergent resistance to the extent that the gloss of the-films is maintained by ordinary cleanings by using detergents, and removability so that they can easily be removed by chemical processes, not by physical removals, when heavily stained or damaged. Since the durability of the films and the removability of the films are properties inconsistent with each other, attempts have been made to achieve both of the properties so as to form films having excellent removability and durability.
For that purpose, coating compositions comprising an emulsified copolymer added with a polyvalent metal complex have been proposed (Japanese Patent Unexamined Publication No. (Sho)47-14019/1972). However, when the compositions containing a polyvalent metal complex are applied and dried, they have problems to generate an odor of amines or ammonia by vaporization of amines or ammonia contained as ligands in the complex upon the decomposition of the complex. The polyvalent metal complexes used for these coating compositions are complexes of heavy metal such as zinc, cobalt, cadmium, nickel, chromium, zirconium, tin, tungsten and aluminum. They are undesirable from the view point of environmental pollution. As a method for preventing the odor of amine after applications of coating compositions, a process has been proposed in which zinc oxide is dispersed in a polymer emulsion (Japanese Patent Unexamined Publication No. (Sho) 57-117552/1982). This method is characterized by comprising a step of dispersing zinc oxide in an emulsion containing an acrylic copolymer by, for example, agitation, by which the resulting coating compositions are stable and free-from the odor of amine upon dryness. However, since zinc used in the composition is a heavy metal, they are undesirable from the viewpoint of environmental hygiene. In addition, since zinc oxide is extremely insoluble in water, zinc oxide can hardly be transferred into polymer oil particles in the emulsion. Zinc oxide sometimes precipitates where the emulsion is left stand for a prolonged period of time.
In order to solve the latter problem, compositions have also been proposed which are obtained by reacting a transition metal with a polymer at a certain temperature (Japanese Patent Unexamined Publication No.(Hei)2-219863/1990). However, metals used in the composition are heavy metals such as zinc, which are undesirable from the standpoint of environmental pollution. Japanese Patent Unexamined Publication No.(Hei)2-219863/1990 also discloses that metals other than heavy metals, e.g., a divalent alkali earth metal, are unsuitable where they are used as crosslinking agents. Furthermore, Japanese Patent Publication No.(Sho)47-15597/1972 discloses aqueous polishing compositions containing calcium chloride or calcium acetate as a divalent calcium salt. It also discloses that these calcium compounds are used in an amount sufficient to ionically crosslink to carboxyl groups contained in the dried compositions. However, this publication merely teaches that calcium compounds are added for modifications before an application of the composition, and it does not disclose that calcium compounds react with the carboxyl groups of the polymer in oil particles of the emulsion.
Accordingly, an object of the invention is to provide stable coating compositions which do not contain any heavy metal and can form tough films without generating an odor of amine or ammonia when they are applied and dried.